Confusion with Probability

 There were some things that stumped me with probability.....

Mutually Exclusive Events-  If an event A occurs then event B cannot occur; if they have no elements in common

This was confusing to grasp but I understood the concept by looking up another definition online.  Basically Mutually Exclusive means that two events are unable to be true at the same time

 I liked this picture because it shows the Venn diagram of events A and B and how they can not intersect with on another.  The probability of events A and B in union is adding event A and event B. 

Next word problems......

Word problems have always been a problem for me all throughout learning math!  I am a very visual person and need pictures and diagrams to understand.  Here is an example of a word problem that stumped me:

* There is a pond of frogs and 50 frogs are caught, marked, and thrown back into the pond.  Then there were 80 frogs caught and 20 of them were marked. What is the population of the pond?

To solve this problem we make a proportion:
20/80=50/x    
 This proportion is comparing frogs marked to the starting number of frogs in the pond and x is the total pond population.
20x=4000
x=200 total frogs in pond

So once I visually made a picture in my head, this proportion made sense for solving the problem.

These two concepts were difficult for me to understand but with manipulatives I was able to grasp the idea!

                                                        
 
http://www.mathsisfun.com/data/probability-events-mutually-exclusive.html
This link helped me with the definition of mutually exclusive events and gave me examples as well!